Using Spline

Spline is the NuGet package published from this repository. It exposes the reusable spline engine without bringing the Avalonia UI layer along with it.

Package and namespace

NuGet package ID: Spline
Assembly: Spline.dll
Public namespace: Spline

The package, assembly, and public namespace are aligned as Spline. Because the namespace and the main spline type now share the same identifier, an alias such as using SplinePath = global::Spline.Spline; keeps consumer code clear.

Included responsibilities

vector math through Vec2
Bezier helpers such as BezierPath and CubicBezier
curvature-oriented fair-spline solving through Spline, TwoParamCurve, and TwoParamSpline
CAD-style global cubic B-spline interpolation through GlobalBSpline
canonical B-spline geometry/evaluation through BSplineCurve
curve-grid interpolation through CurveGrid and TwoCubics
headless polyline simplification with PolylineUtils

Excluded responsibilities

application settings persistence
Avalonia windows, views, and interaction logic
demo-specific editing and visualization behavior
product-specific CAD file parsing/serialization

Packaging model

The package is built from src/Spline/Spline.csproj and includes both a NuGet package and a symbol package during dotnet pack.

Fair-spline consumer flow

using Spline;
using SplinePath = global::Spline.Spline;

var controlPoints = new[]
{
    new SplinePath.CP(new Vec2(0, 0), "corner", null, null),
    new SplinePath.CP(new Vec2(60, 20), "smooth", null, null),
    new SplinePath.CP(new Vec2(120, 0), "corner", null, null),
};

var spline = new SplinePath(controlPoints, isClosed: false);
spline.Solve();
spline.ComputeCurvatureBlending();

BezierPath path = spline.Render();
string svg = path.ToSvgPath();

CAD-style B-spline consumer flow

using Spline;

var fitPoints = new[]
{
    new Vec2(0, 0),
    new Vec2(60, 40),
    new Vec2(120, 10),
    new Vec2(180, 0),
};

var result = GlobalBSpline.InterpolateDetailed(
    fitPoints,
    startTangent: new Vec2(1, 0.2),
    endTangent: new Vec2(1, -0.1));

BSplineCurve curve = result.Curve;

IReadOnlyList<Vec2> cadControlPoints = curve.ControlPoints;
IReadOnlyList<double> knots = curve.Knots;
IReadOnlyList<double> weights = curve.Weights;

string svg = curve.ToSvgPath();

Use GlobalBSpline when fit-point interpolation must produce explicit B-spline degree/control-point/knot semantics. Use the existing Spline solver when its curvature-oriented fairing behavior and editing model are the desired contract.

When to use DemoSpline instead

Reach for samples/DemoSpline when you need:

interactive editing and tangent manipulation
freehand tracing and curve fitting validation
tuner-based exploration of CurveGrid and TwoCubics
live confirmation that a package change still behaves as expected

For a focused headless example of CAD-style interpolation, use samples/GlobalBSplineSample.